Re: cutting an image into multiple images
Re: cutting an image into multiple images
- Subject: Re: cutting an image into multiple images
- From: Ken Thomases <email@hidden>
- Date: Sat, 21 Jun 2008 18:47:04 -0500
On Jun 21, 2008, at 8:41 AM, Dharmendra wrote:
I am trying to get a user-defined image in specific format (m x nm)
and want
to generate an array with count n containing m x m sized images. I
have
written the following code, but would like to know if there is
better way to
do the same:
Rather than using NSImage, which is really about drawing, you might
consider using NSBitmapImageRep directly. Initialize the source from
the file data. Then, initialize each sub-image using one of the
initWithBitmapDataPlanes:... methods, obtaining the arguments by
querying the source and performing a bit of math on the planes value.
That said, read the caveat in the NSBitmapImageRep class overview:
Alpha Premultiplication
If a coverage (alpha) plane exists, a bitmap’s color components are
premultiplied with it. If you modify the contents of the bitmap, you
are therefore responsible for premultiplying the data. For this
reason, though, if you want to manipulate the actual data, an
NSBitmapImageRep object is not recommended for storage. If you need
to work with unpremultiplied data, you should use Quartz,
specifically CGImageCreate with kCGImageAlphaLast.
That caveat would apply to NSImage, too, because it's based on
NSBitmapImageRep.
Cheers,
Ken_______________________________________________
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